From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3E4EA3A4515 for ; Fri, 6 Mar 2026 13:49:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772804976; cv=none; b=NEWnqHJkLUyB90h/Q1/ihaR6hdtwiWxbEVcXMU/UlmFKhy3XaruRkC6dz8BxmyZ1QNrRFFAjLCeVHvvYF3wNC+oZyNq5f5070HJamJ2PQ2ptmls57JSu7IuojXV2QOj7SEm3ZO+5c6amhfq0G4+s6naMx9nAwVT7x8OqYZgs26o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772804976; c=relaxed/simple; bh=irOuPnqtfg3b/SaxHjIDOK3emq7XQZuod4JIYQGwsI0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cIIR52SaheGEeMFtDQgpKjqvGY/fpFXsft2b6+1U+BI2G6qpq1eLc98ACgfE0KsGnccEjsFbvt4+Tjyhl0rO89j7n2um7d1haW5nn6ng6hHFPN7pwX8872lcLycNaEE+BmJRkgpO25EjCSBbF8CjL1xGx3Gft8ZyE40uoInz7T4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oxRUEyPD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oxRUEyPD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B110C4CEF7; Fri, 6 Mar 2026 13:49:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772804975; bh=irOuPnqtfg3b/SaxHjIDOK3emq7XQZuod4JIYQGwsI0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=oxRUEyPDum7HCDI0i9m+D1kN2UUcv7bGDNu06MEpelNeSK0caUq6J8rXGgksSmgj9 QJfRAQ7UULSbl2fn/6qyoLO6VSkYg1jcOMl3oqLnLlFguufUHVdjaQxHByMwCDQaFp /OUWbTzGykXwFIZ5eH5t95j1oB+pMiEiCZcTS/o9hF2PhaXmZpSRP2ldfQVucIklG/ o9U+SiDeEyD8vihv4rjvxPdvUpYrhnpER2Eu8UQ331kd/HUTYgrlsXNIeTmiWLvMQO Ro6cA1l3zdgawtAikWWHNqtBPPlYKTT/g5q53yFc6LO1xVvpO80OgxbgtqWKdf3BqX SDg6nKcbSa6pw== Message-ID: Date: Fri, 6 Mar 2026 14:49:27 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: migrate: requeue destination folio on deferred split queue To: Usama Arif , Andrew Morton , npache@redhat.com, ziy@nvidia.com, linux-mm@kvack.org Cc: matthew.brost@intel.com, joshua.hahnjy@gmail.com, hannes@cmpxchg.org, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-kernel@vger.kernel.org, kernel-team@meta.com References: <20260306133556.2051251-1-usama.arif@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/6/26 14:35, Usama Arif wrote: > During folio migration, __folio_migrate_mapping() removes the source > folio from the deferred split queue, but the destination folio is never > re-queued. This causes underutilized THPs to escape the shrinker after > NUMA migration, since they silently drop off the deferred split list. > > Fix this by calling deferred_split_folio() on the destination folio > after a successful migration, for large rmappable folios. > > Reported-by: Johannes Weiner > Fixes: dafff3f4c850 ("mm: split underused THPs") > Signed-off-by: Usama Arif > --- > mm/migrate.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index ece77ccb2ec0..98d0a594f7b7 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1393,6 +1393,17 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private, > if (old_page_state & PAGE_WAS_MAPPED) > remove_migration_ptes(src, dst, 0); > > + /* > + * Requeue the destination folio on the deferred split queue if > + * the source was a large folio that was on the queue. Without > + * this, NUMA migration causes underutilized THPs to escape > + * the shrinker since the source is unqueued in > + * __folio_migrate_mapping() and the destination is never > + * re-queued. > + */ > + if (folio_test_large(dst) && folio_test_large_rmappable(dst)) > + deferred_split_folio(dst, false); Doesn't that mean that you will readd any large folios, even if already previously taken off the list after scanning? So I am not sure if your "if the source was a large folio that was on the queue." comment is accurate? -- Cheers, David